The Basque tense and aspect system is complicated by the co-existence
of two conjugation types which allow for different oppositions. One is
the conjugation of analytically (periphrastically) construed verbs,
the default case, the other involves a small number of synthetically
construed verbs, which can optionally be construed periphrastically as
well.

Here is an example for both conjugation types. The analytical
construction consists of a main verb in a non-finite form (here the
verbal noun in the inessive case) and a tense-aspect auxiliary (here
the present tense of the transitive auxiliary ukan):1

In comparison with early records (16th century) the number of synthetically construed verbs has significantly decreased.4

1. Tense-aspect oppositions with analytical verbs

The analytical construction is the only productive pattern, i.e.
the analytical verb represents the normal case.

1.1. Using present-tense auxiliaries
1.1.1. Present
By combining the auxiliary in the present tense with the nominalized main verb (verbal noun) in the inessive, we get the normal
present tense, as can be seen in example (1). Example (3) shows
the case of an intransitive verb:

(3) Mintza-tze-n naiz. 'I speak.'
speak-NOM-IN PRS.1S

1.1.2. Present perfect
The combination of the present-tense auxiliary with the participle
is used to mark perfect tense. It means that the event expressed
by the main verb has taken place a short time ago:5

1.1.3. Resultative
Such adverbials are possible, if the participle is used like an
adjective with the individualizer -a (usually called 'article'),6
which makes it accessible for number agreement with the head NP:7

The resultative is used, when the speaker wants to underline that
an action or situation in the past is still relevant at the time
of speech.

1.1.4. Future
Future is expressed by adding the delimitative case ending -ko8 to
the participle. After consonants, some dialects prefer the (possessive) genitive -en instead (I gloss them as future markers,
when attached to participles):

1.2. Using past-tense auxiliaries
In its turn the past-tense auxiliary can be combined with the same
range of non-finite forms as the present tense. This results in
the following tense-aspect meanings:

1.2.1. Imperfective past
When combined with the verbal noun in the inessive (the combination denoting simple present above), the past auxiliary is used
to express imperfective past tense:

Thus, the formal opposition between verbal noun and participle
distinguishes imperfective and perfective aspect in the past,
whereas in the present tense it is used for distinguishing simple
present and perfect. This is summarized in the following table:

Of course, the pluperfect can be interpreted as a resultative in
the past, as the event in question is always seen to be relevant
to another (later) event in the past.

1.2.4. Future of the past
The auxiliary can be combined with the non-finite future form
(i.e. participle + delimitative or genitive) to form a secondary
future tense which is used in subordinate clauses, when the main
clause is in the past (consecutio temporum):10

Note that the opposition between simple present and present perfect (a temporal opposition) is parallelled by the opposition of
imperfective and perfective aspect in the past.

2. Tense-aspect oppositions with synthetical verbs

We can conjugate synthetical verbs (enumerated above) directly, by
attaching person and tense markers to the verbal root. They may
also be analytically construed. That means that we have an add-
itional formal and functional opposition between such verbs con-
strued synthetically and the same verbs construed analytically. As
we shall see, some tenses and aspects cannot be expressed synthet-
ically.

2.1. Synthetical construction
2.1.1. Present
The synthetical verb has a present-tense form, which (just like
the present tense of analytical verbs) is neutral with respect to
the aspect opposition:

(17) Ba-nago. 'I stay.'
ENC-stay:PRS.1S

The unmarked case of a synthetical verb in the present tense would
be to construe it synthetically.

2.1.2. Past
Analogously, a past tense can be formed, which (contrary to the
analytical form) is aspectually neutral, i.e. it can always be
used, when we would otherwise have to decide between perfective
and imperfective forms in the analytical construction.

(18) Ba-nengoen. 'I stayed.'
ENC-stay:PRT.1S

Especially those dialects that have been under long and heavy Romance influence (e.g. the Eastern dialects of Lower Navarra) prefer
the analytical construction in the past, whereas in the present
tense, synthetically construed verbs may be found to some extent
(even in potential and conditional forms). The reason for this may
be that in Romance the distinction of perfective and imperfective
aspect is obligatory in the past tense. In general, synthetical
forms tend to disappear first for the past tense and last in the
imperative. Note also that the verbs still showing synthetical
conjugation are movement verbs or verbs with stative semantics,
i.e. verbs that do not express actions or - more generally speaking - a change of situation. They are verbs where the distinction
of perfective and imperfective aspect only makes sense, if special
meanings are involved (e.g. 'to know' -> 'to come to know').

2.2. Analytical construction
Formally, the analytical construction of synthetical verbs is the
same as for analytical verbs. As analytical forms and synthetical
forms stand in opposition to each other, their semantic value (or
'function') is different.

2.2.1. Using present-tense auxiliaries
2.2.1.1. Present progressive
If a synthetical verb would normally be used synthetically, the
use of the analytical construction in the present tense (present
auxiliary + verbal noun) will express a specific aspectual meaning, in most cases progressive:

2.2.1.2. Present perfect
The present auxiliary combined with the participle is again used
as a perfect:

(20) Egon naiz. 'I have come.'
stay:PCP PRS.1S

The perfect can only be formed analytically.

2.2.1.3. Resultative
The same holds for the resultative:

(21) Joan-a da. 'S/he is gone.'
go:PCP-ART PRS.3S

Compare this sentence with the following in the present perfect:

(22) Joan da. 'S/he has (is) gone.'
go:PCP PRS.3S

This sentence can have a resultative meaning, but normally refers
to an event in the near past (meaning e.g. 'S/he has gone (there)
this morning.'), whereas joana da means something like: 'S/he is
in the state of being gone.'

2.2.1.4. Future
In the modern language, the future can only be formed periphrastically by attaching the delimitative (or genitive) to the participle, as has been illustrated above:

2.2.2. Using past-tense auxiliaries
When synthetically used, the synthetical verb is aspectually neutral in the past tense, as it is in the present. It does not interfere with the aspectual opposition between perfective and imperfective past, expressed by the inessive verbal noun and the
participle respectively, both combined with a past tense auxiliary.

2.2.2.1. Imperfective past
Instead of the aspectually neutral form (ba-)nindoan ('I went.'),
the following form is usually preferred, when the event is viewed
as on-going at some point of reference or as iterative, i.e. imperfective:

(24) Joa(i)-te-n nintzen 'I went (was going).'
go-NOM-IN PRT.1S

2.2.2.2. Perfective past
If the event is viewed as completed and punctual, i.e. perfective,
the following analytical construction (the same as with analytical
verbs) is preferred over the simple past:

Although this article is primarily about tense and aspect in
Basque, I shall mention mood as well, without going into detail,
just to give a view of the whole.

3.1. Subjunctive
Except for the third person, the subjunctive is formally identical
with the imperative. Basically, it is used in subordinate clauses
that depend on a main clause with a verb of wishing or order. The
event for which it is used is presented as non-real, but desired.
Only the tense-aspect auxiliaries (izan and ukan) have special
subjunctive forms. They are suppletive: for izan, the root -di- is
used (grammarians speak of a subjunctive verb *edin, which, of
course, has no participle), for ukan the root -za- (grammarians
speak of a subjunctive verb *ezan). Here is an example:

The subjunctive is not used with the participle, but with the non-
finite verbal stem, which is homophonous with the participle, if
it ends on -n. If the verb has an -i- or -tu-participle (only the
latter being productive), the difference becomes evident:

Inserted into past tense forms, -ke- marks the conditional, which
is mainly used in the apodosis of unreal conditional clauses and
thus corresponds to the conditional of Romance languages, or of
English; note that additionally in modern Basque, the non-finite
part of the analytical construction is marked for future:13

It is commonly thought (and philologically substantiable) that
-ke- was originally a future marker. Due to the modal component of
the future, it could develop into a mood marker, when a new analytical future came up.

The semantics of the delimitative makes us think that the analytical future was originally restricted to near future (event 'on
the edge of' (delimitative!) occurrence).

4. Conclusion

We have seen that synthetical verbs show a set of tense-aspect oppositions that differ from the tense-aspect oppostions of analytical verbs. The former oppose an aspectually neutral, simple
present to a progressive (habitual) one and have an aspectually
neutral past tense that does not exist for analytical verbs.

All synthetical verbs are old ones. The number of such verbs has
been decreasing over the last centuries up to the point that in
some dialects they have almost disappeared altogether. It is
plausible to assume that before the first written sources, Basque
had had more synthetical verbs. It is even probable that the analytical construction is an innovation that came about in a (pre-)
romance language contact situation, most probably originating from
spoken Latin. The reason for such an assumption is the structural
similarity with the habeo-factum perfect which is typical of vulgar (or spoken) Latin. The Latin construction, which is used instead of the simple past for resultative events, consists of the
verb 'to have' (habeo 'I have', at that time pronounced something
like /ajo/) and the participle (e.g. factum 'done', habeo factum
'I have done'). Due to language contact this construction has
spread into adjacent Germanic and Slavic languages, being otherwise uncommon among the languages of the world which, so far, have
not inherited it from European languages. The productive participle ending -tu corroborates the assumption that the Basque perfect construction comes from Latin.

The evolution of the analytical present is comparable to what happens in quite a number of languages:15 In order to denote progressive aspect, the verbal noun is used in a locative case (here the
inessive) together with a verb meaning 'to be', i.e. 'to be in/at
an action'. The specialty of Basque is that both 'to be' and 'to
have' are used with the inessive verbal noun, according to the actant structure of the verb.16 This 'anomaly' with respect to other
languages with a structurally similar progressive can be explained
by the fact that the distinction of the two auxiliaries is necessary to clearly mark the actant structure.

The progressive meaning gets lost with the decline of a regular
opposition between analytical and synthetical forms.

The analytical construction revolutionized the tense-aspect system
as a whole. New tense-aspect oppositions evolved (near past vs.
remote past, perfective vs. imperfective etc.); a new analytical
future was introduced (perhaps a near future in the beginning),
which came to stand in opposition to a potential future developing
into a merely modal category (potential, conditional). Moreover,
the auxiliary suppletion (izan vs. *edin (intransitive, 'to be')
and ukan vs. *ezan (transitive, 'to have'), perhaps different
verbs once) allowed for a regular distinction of indicative and
subjunctive mood.

The following table gives a synoptic view of the tense-aspect
system and its evolution. The small (and probably still decreasing) number of synthetical verbs are treated as relicts from Classical Basque and therefore neglected under "Modern Basque":17

The present situation of Basque is somewhat in between stage 1 and
2, as it still shows some synthetically construed verbs, incidently less in the past tense. As already said, the reason for this
may be the obligatory past perfective/imperfective distinction in
the Romance contact languages. On the whole, the stage 2 system
comes very near to the Romance system.

We can conclude that the change of the Basque tense-aspect system
is contact-induced. The most significant step that made all the
other steps follow, was the introduction of the analytical construction, probably on the model of spoken Latin.

If we compare this evolution with what had happened in other
spheres of Basque grammar, we find that the tense-aspect system is
particularly innovative, Basque morphosyntax being otherwise very
conservative.18 A reason for this may be that tense-aspect oppositions have very concrete semantic meaning. This 'semantic load'
makes bilingual speakers feel the necessity to transpose structure
from one language into the other, all the more as they found
'meaningful' material (e.g. a verb 'to have') which could be
translated without much difficulty and thus be used as a basis of
structural transpositions ('calques').

ukan, the participle form of the verb (usually the citation
form), is used in the North Eastern dialects only. Basque grammarians therefore reconstructed a more regular participle form
*edun, which is used in some grammars to refer to that auxiliary.

The enunciative ba- is obligatory, if a conjugated verb stands
at the beginning of the sentence. It fills the empty focus
position which comes canonically before the conjugated verb.

d-u-t can be analyzed in the same way, -u- being the transitive
root. Especially in the auxiliaries, we have to deal with a
great deal of fusion, all the more as the forms become more
complex. I shall therefore refrain from a detailed interlinear
analysis. The actant structure will be visualized as in (1),
where the ergative is indicated by the open side of the pointed
bracket (LAFON (1943) lists about 60 in texts of the 16th and 17th
century.

i.e. what may be called a "recent perfect" (cf. BREU 1988).

That the 'article' is actually an individualizer is shown by
ITURRIOZ (1982, 1985); unfortunately, Basque grammarians and
school teachers keep on speaking of "mugagabea" ('indetermined')
and "mugatua" ('determined'), in spite of better knowledge.

There are concurrent ways of formation: In North-Eastern
dialects, the partitive -rik is attach to the participle, in the
South-Western dialects a special formative -(e)ta is added,
which may be etymologically related to eta 'and'. HAASE (1991a)
studies the resultative in greater detail. HAASE (1991b) gives a
short account of the development in contact with Gascon and
French, where the resultative came to be a passive.

It may be reinforced by adding the participle izan(a) (or
ukan(a) in transitive clauses, where this form exists). This
seems to be a 'calque' from the neighboring Romance languages.
The participles izan and ukan may also be added to the simple
past tense, in order to signalize non-resultative anterior.

Sometimes normal future may be found in sentences like the
following, if the event in the subordinate clause is still going
to happen.

There are less grammaticized ways of expressing progressive
and habitual aspectuality, using the operator verbs ari ('to be
occupied with') and ohi ('to be used to').

The main clause may be left out elliptically.

In the dialects of the North-East and in older texts, the
subjunctive is combined with -ke-, which is used with the verbal
stem, if the construction is analytical. This is not the place
to treat conditional clauses at length; for that matter, see
OYHARABAL (1987).

The suppositive (SUP) is a variant of the past without the
ending -(e)n, used in if-clauses.